This invention relates to a portable phone such as a portable digital portable phone or a PHS (Personal Handy phone System) phone and, particularly, to a portable phone having a recording function such that call-audio is converted into digital data and recorded as the digital data.
In case where a user of the portable phone makes or receives a call when he is on the move, it is frequently difficult to take notes of the contents of a call. To get rid of such inconveniences, the portable phone generally has a recording or a memorizing function to make a record of the contents of the call (call-audio). Such a portable phone having a recording function is disclosed in for example, Japanese Unexamined Patent Publications (JP-A) No. 13243/1998.
A portable phone of the type described in the publication has a codec-(coder-decordr), a microphone, a receiver (speaker), a DSP (Digital Signal Processor), a radio unit, a key, a display, and a central processing unit. An antenna is connected to the radio unit. A memory is connected to the central processing unit.
During the call, the central processing unit controls the recording and reproduction of audio data in accordance with the operation inputted by the key. Specifically, when the command for recording the audio is given by the operation of the key, the central processing unit stores the audio data which was encoded by the codec and compressed by the DSP and/or stores compressed audio data which was received by the radio unit and demodulated by the DSP in the memory. When the command for reproducing the audio is given by the operation of the key, under the control of the central processing unit, the audio data which was taken out from the memory is expanded by the DSP and changed into an analogue audio by the codec and then reproduced by the receiver.
By the use of the portable phone as described, the user can record, whenever there is a need, the content of the call by a simple operation of the keys and thereafter reproduce and check the recorded contents. However, the portable phone can make a record of the call only when the user gives a recording command so that the recording starts after the key operation by the user. In order to make a record of a call before the recording operation has started, the user, either a receiver or a caller, should repeat the conversation such that the extra time is required for a wasteful communication.
For example, Japanese Unexamined Utility Model Publication (A) No. 113361/1988 and Japanese Unexamined Patent Publication (A) No. 298123/1990 disclose methods to overcome the above-mentioned drawback.
The utility model publication describes a “telephone having a recording function” having a cassette tape recorder which accommodates an endless tape therein. When a receiver is picked up, the telephone set automatically starts recording a call. The user of the telephone set can reproduce the endless tape and repeat the conversation to check the contents of the call.
The patent publication describes a “radio set” which changes every received audio signal into digital signal and which successively records the digital signal into a memory and, upon the request by the user, reads out the contents of the memory and reproduces the contents as speech signal. The recording of audio signal automatically restarts as the reproduction of the contents in the memory is completed.
However, the above-mentioned publications have the following problems. Because the telephone having the record function is provided with the cassette tape recorder, the telephone is large and therefore unsuitable. In the radio set, in case where the recording time exceeds the total recording capacity of the memory, the contents which have been recorded earlier are deleted in order of recordation. In this event, it may be impossible to listen and check the earlier recorded contents. Although this drawback will be overcome if a memory having a huge recording capacity as the endless memory is provided, such an apparatus is increased in cost and may require long time to access to the desired contents.
Furthermore, in the method of reproducing the contents as speech signal, it is not possible to record nor hear the newly given information during the recorded contents are reproduced.